The treatment of nitrogen-deficient agriculture wastewater, arising from the vegetable and fruit processing, is a significant problem that limits the efficiency of its biological treatment. This ...study evaluates the effectiveness of the symbiotic co-culture of Azospirillum brasilense and Scenedesmus sp., under two nitrogen levels (8.23 mg L−1 and 41.17 mg L−1) and mixing systems (aeration and magnetic stirring), aiming to simultaneously use the N-deficient media for their growth while producing biomass for biofuels. Microalgae growth and biomass composition, in terms of protein, carbohydrate and fatty acid contents, were evaluated at the end of the exponential growth phase (15 days after inoculation). Results show that the symbiotic co-culture of microalgae-bacteria can be effectively performed on nitrogen-deficient media and has the potential to enhance microalgae colony size and the fatty acid content of biomass for biofuels. The highest biomass concentration (103 ± 2 mg·L−1) was obtained under aeration, with low nitrogen concentration, in the presence of A. brasilense. In particular, aeration contributed to, on average, a higher fatty acid content (48 ± 7% dry weight (DW)) and higher colony size (164 ± 21 µm2) than mechanical stirring (with 39 ± 2% DW and 134 ± 21 µm2, respectively) because aeration contribute to better mass transfer of gases in the culture. Also, co-culturing contributed in average, to higher colony size (155 ± 21 µm2) than without A. brasilense (143 ± 21 µm2). Moreover, using nitrogen deficient wastewater as the culture media can contribute to decrease nitrogen and energy inputs. Additionally, A. brasilense is approved and already extensively used in agriculture and wastewater treatment, without known environmental or health issues, simplifying the biomass processing for the desired application.
The need to decarbonize industrial processes and to increase the utilization of renewable resources, either energy and raw materials, has led to the development of new production processes. The focus ...of this paper is to evaluate the environmental impacts of an innovative 1 kW pilot plant for methane production, following the life cycle thinking approach. The process is based on the coupling of an alkaline water electrolysis, which generates syngas using a carbon source, with a methanation reactor that converts the syngas to methane. The life cycle assessment (LCA) takes into account the pilot plant construction materials, electricity and reactants used, for a functional model of a mole of methane produced per hour of operation. Data from the pilot plant, in particular reaction conversions, were used complemented with data from the literature and inventory databases. Energy and the construction materials used to build the experimental unit are the main factors influencing the environmental performance. Several scenarios were defined varying the electricity source and the carbon source, showing the results that the energy source is more relevant to reduce the process environmental impacts. The results can be used to scale-up and to better implement the combined electrolysis methanation process in industrial practice.
•A Life Cycle Assessment of methane production in an innovative combined electrolyzer/methanation reactor process was done.•Energy and construction materials are the main factors influencing the environmental performance.•Several scenarios were analyzed varying the energy source and carbon source.•Replacing the energy source to fully renewable has the largest reduction of the environmental impact.
Adding value to agro-industrial residues is becoming increasingly important, satisfying needs to promote resources’ use efficiency and a more sustainable and circular economy. This work performs a ...parametric and kinetic study of enzymatic esterification of lard and tallow with high acidity, obtained by the rendering of slaughter by-products, allowing their use as a feed ingredient and increasing their market value. After an initial analysis of potential enzyme candidates, a Candida antarctica lipase B was selected as a biocatalyst for converting free fatty acids (FFA) to esters, using excess ethanol as the reagent. Results show that the fat acidity can be reduced by at least 67% in up to 3 h of reaction time at 45 °C, using the mass ratios of 3.25 ethanol/FFA and 0.0060 enzyme/fat. Kinetic modelling shows an irreversible second-order rate law, function of FFA, and ethanol concentration better fitting the experimental results. Activation energy is 54.7 kJ/mol and pre-exponential factor is 4.6 × 106 L mol−1 min−1.
This work aims to evaluate the water footprint of microalgae cultivation in a closed pilot-scale multi-tubular photobioreactor, taking into account the life cycle stages of reactor construction and ...its operation for microalgae cultivation, on a gate-to-gate approach. The data was obtained from real production conditions complemented with data from the literature and life cycle inventory databases. Results indicate that the total water footprint lies in the range of 2.4-6.8 m3/kg dry biomass, being the PBR operation stage responsible for the largest contribution (> 60 %), mainly due to water consumption associated to electricity and nutrients production for the PBR operation.
Recently, perovskite solar cells (PSCs) emerged and promise to break the prevailing solar energy paradigm by combining both low-cost and high-efficiency. PSC technology actually shivered the solar ...photovoltaic (PV) community as a strong candidate to rival the efficiency of traditional PV devices; in less than 12 years its efficiency was improved from 3.8% to almost 26%. Despite the tremendous and successful effort for obtaining PSC devices with high power conversion efficiencies, little efforts have been devoted to study fundamental engineering aspects essential for future industrial production. In particular, this work makes an analysis of the energy consumed and the carbon footprint of producing a 3-mesoscopic PSC 8 × 8 cm2 module with an 8.7% efficiency in a life cycle perspective. A “cradle-to-gate” study was performed, using as much as possible primary data. Considering the PSC module as the functional unit the results show that the mesoporous layer deposition is the dominant term concerning the energy consumption. Regarding the carbon footprint, the gold layer, in particular gold, is the main factor. Changing the electricity source to renewable photovoltaic energy reduces significantly the carbon footprint. The results stress the need to replace gold, and use less severe operational conditions in the module production.
•The carbon footprint and energy consumption of a 8 × 8 cm2 perovskite solar cell were evaluated based on LCA methodology.•The deposition of the mesoporous layer is the principal energy consumption term.•The gold layer, in particular gold extraction, dominates the carbon footprint.•Using fully renewable energy in the process reduces significantly the carbon footprint.
Food waste is a significant problem requiring appropriate disposal measures. Waste valorization via high-value component extraction is one of the most interesting solutions, as natural food additives ...are expected to be healthier and more sustainable than synthetic ones. Yet, the selection of the most adequate disposal option should take into account both the economic and environmental aspects. Thus, in this work the life cycle energy consumption and carbon emissions of the extraction of ergosterol from mushroom residues is assessed. To support the development of a natural ergosterol extraction process, a cradle-to-gate study was done, for a functional unit of 1 g of extract. Data was obtained from a lab-scale experimental unit, complemented with literature data and life cycle environmental data from EcoInvent V3.3. Both CED and IPCC 2013 methods were used. Results show that lyophilization, evaporation and ultrasound assisted extraction are the processes with the highest carbon emissions and primary energy. Moreover, electricity, which supports most processes, was shown to be a key hotspot for improvement. Thus, two alternative scenarios with electricity mix and source (local photovoltaic production) were considered. Results showed that local photovoltaic production can potentially reduce non-renewable primary energy by 77% and carbon emissions by 83%.
•Ergosterol extraction from mushroom residues is analyzed.•The life cycle (LC) energy and carbon emissions are determined.•Lyophilization, evaporation and UAE have the largest LC energy and carbon emissions.•Local PV electricity reduces carbon emissions (83%) and non-renewable energy (77%).
Ultraviolet radiation (UVR; 280–400 nm) has a great impact on aquatic ecosystems by affecting ecophysiological and biogeochemical processes as a consequence of the global change scenario generated by ...anthropogenic activities. We studied the effect of PAR (P)+UVA (A)+UVB (B) i.e. PAB, on the molecular physiology of the unicellular green alga
Dunaliella tertiolecta
for six days. We assessed the relationship between the triggered UVR stress response and metacaspases and caspase-like (CL)activities, which are proteases denoted to participate in cell death (CD) in phytoplankton. UVR inhibited cell growth and
in vivo
chlorophyll a fluorescence but did not cause cell death. Western blot analyses reflected that Type-II metacaspases (MCs) are present and appear to be involved in UVR induced-cell stress but not in dark-induced CD in
D. tertiolecta
. Enzyme kinetics revealed that cleavage of the MCs-reporter substrates RVRR, QRR, GRR, LKR, HEK, and VLK was 10-fold higher than WEHD, DEVD, IETD, and LETD CLs-substrates. The lowest apparent Michaelis-Menten constants (K
M
ap
) corresponded to RVRRase (37.5 μM) indicating a high affinity by the RVRR substrate. The inhibition of enzymatic activities by using inhibitors with different target sites for hydrolyses demonstrated that from all of the R/ Kase activities only RVRRase was a potential candidate for being a metacaspase. In parallel, zymograms and peptide-mass fingerprinting analyses revealed the identities of such Rase activities suggesting an indirect evidence of possible natural physiological substrates of MCs. We present evidence of type II-MCs not being involved in CD in
D. tertiolecta
, but rather in survival strategies under the stressful irradiance conditions applied in this study.
Framework for Sustainability Metrics Martins, António A; Mata, Teresa M; Costa, Carlos A. V ...
Industrial & engineering chemistry research,
05/2007, Letnik:
46, Številka:
10
Journal Article
Recenzirano
This work presents the application of a new framework for sustainability metrics to industrial processes, in particular, to chemical processes. The sustainability of an industrial process can be ...evaluated using a set of three-dimensional (3D) indicators that represent all three dimensions of sustainability: economic, environmental, and societal. The four 3D metrics proposed in this worknamely, material intensity, energy intensity, potential chemical risk, and potential environmental impactare applicable to a wide range of process systems. The first two metrics are associated with the process operation. The remaining two metrics, potential chemical risk and potential environmental impact, respectively represent chemical risk to human health in the process environment, and the potential environmental impact of the process on the surrounding environment. To illustrate this framework and the applicability of the proposed set of 3D metrics, two case studies are presented: chlorine production process using three different alternatives (membrane, diaphragm, and mercury cells), and the separation of an acetone/chloroform mixture by two different solvents (benzene and methyl-n-pentyl-ether). Results of this study show that this framework can be effective in selecting the more-sustainable process by comparing process alternatives.
This work aims to evaluate the carbon footprint (CF) of microalgae production in a closed pilot-scale multi-tubular photobioreactor (PBR), on a gate-to-gate approach. Primary data from real ...production conditions complemented with data from the literature and life cycle inventory databases was used. The carbon embedded in the PBR’s construction materials and nutrients necessary for the microalgae growth were considered. A global CF of 68.34 kg CO2-eq/kg dry biomass was obtained. A CF of 1.72 kg CO2-eq/kg dry biomass was calculated for the PBR construction stage, contributing to 3 % of the overall value. For 74 kg of dry biomass/year produced with this PBR, the CF for this stage was 66.62 kg CO2-eq/kg dry biomass, corresponding to 97 % of the total global CF. In this study, electricity production for the reactor operation is the major contributor (79 %) to the overall CF, followed by the production of nutrients used to prepare the culture medium (21 %). CO2 fixation by microalgae reduces the global value by 3 %.
This work presents experimental results on alkali and enzymatic catalysis of corn oil into biodiesel with an optimization of operating conditions and further experiments on enzyme reuse. A comparison ...of the alkali-catalyzed methanolysis and ethanolysis of corn oil is done, followed by the study of the enzymatic-catalyzed ethanolysis using the alcohol at different concentrations (ethanol absolute, 96%, and 70%, v/v). Results show that the best operating conditions for biodiesel production using absolute ethanol (containing no water) as reagent are an oil/alcohol molar ratio of 1:6, a catalyst/oil weight percentage of 2.8 wt %, a reaction time of 12 h, and a reaction temperature of 35 °C. For these conditions it was possible to obtain a reaction yield of 98.95 wt % with a fatty acid ethyl esters (FAEE) content of 69.2 wt %, with linoleate (C18:2) and oleate (C18:1) being the most significant esters (with relative percentages of 42.97 wt % and 22.54 wt %, respectively). Regarding the evaluation of the enzyme activity loss during reaction, it was concluded that under these conditions it is possible to reuse the enzyme four times after which there was a significant loss of the biodiesel quality according to the EN 14214:2009 standard.
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